America's bridges need greater investment to survive

In the debate over President Joe Biden's infrastructure and climate bill, it was perhaps inevitable that some policymakers would object to including anything other than traditional infrastructure such as roads and bridges. More surprising is what I'll call the "new pundit view," which casts doubt about spending in precisely that narrow category. This is a perspective based on very imperfect data. Especially given the severe weather that climate change is likely to bring, the White House infrastructure and climate plan is right to spend more to repair and improve roads and bridges.

The national news media and politicians typically decry the poor quality of U.S. physical infrastructure, often referring to the abysmal grades it receives from the American Society of Civil Engineers (this year's mark was a C-minus). So you might think Biden's proposed $115 billion investment in roads and bridges would be noncontroversial.

But some pundits are now wondering whether the country's bridges and roads are so bad after all — and therefore whether the infrastructure and climate plan needs to spend so much in this category. As my Bloomberg Opinion colleague Matt Yglesias recently wrote in his "Slow Boring" newsletter:

"There is a lot more happening in Joe Biden's American Jobs Plan than just throwing money at America's crumbling roads and bridges. And it's a good thing, too, because after years of being mildly annoyed by this rhetoric, I've actually been researching it and it's basically a huge myth.

"Not to say that there are zero roads or bridges in the United States that could use a little repair.

"But there's just no reason to believe that the existing surface transportation funding levels in the United States are inadequate."

Kevin Drum had a similar reaction, writing that "U.S. bridges are in … sort of OK shape." This new pundit view highlights data showing that the quality of U.S. infrastructure has not deteriorated recently and that our international infrastructure ranking is "middling" (to use Drum's phrasing), not rock-bottom. Robert Krol from the Mercatus Center at George Mason University came to this view earlier, noting last year that "The condition of major highways and roads is stable. Furthermore, there are fewer bridges in poor condition today than there were five years ago."

The new pundit view is correct that official measures suggest the share of bridges in poor condition has declined. Roughly 60,000 of the nation's more than 600,000 bridges were in "poor" condition in 2009, according to Federal Highway Administration data. By 2020, that number had fallen to 45,000 — even though the number of bridges in the country had grown slightly.

But while the share of bridges in poor condition has declined since 2009, so has the share in good condition, from 47% to 45%. It's reasonable to spend more when the share of bridges in good condition is not only less than half, but shrinking. Why not aim for most bridges to be in good condition?

The proposed infrastructure spending, furthermore, is intended to occur over the next decade. And these backward-looking statistics don't account for what's likely to happen in the future.

Consider the age of American bridges. Not surprisingly, bridge quality tends to diminish as a bridge ages, especially toward the end of its useful life. Today, the average bridge in the U.S. was built in 1975, making the average age 45 years. In 1992, the average age of a bridge was 34 years. And today a quarter of bridges are 60 years old, up from 15% in 1992. As the bridges grow older and a larger share of them approach the end of their useful lives, it will cost more to maintain or replace them than a backward-looking indicator would suggest. Without investment beyond current levels, bridge quality will decline.

The most dramatic event involving a bridge is a collapse. And half of all bridge collapses are caused by "bridge scour." This occurs when sediment around the bridge's foundation is swept away by fast-moving water, creating dangerous "scour holes" that undermine the bridge's structural integrity. While bridges with relatively bad scour ratings are more vulnerable to this type of collapse, more than 80% of scour-related collapses have occurred where the structure had been judged "scour stable." This matters, because climate change is likely to make scour conditions worse. With investment in better monitoring and countermeasures, the risks can be reduced.

Peter R. Orszag is a Bloomberg Opinion columnist.